The “Atom at Interfaces” axis develops research activities along two kinds of "niche" experimental techniques, borne by two teams: the OIA team realizes atom optics and atom interferometry experiments using cooled metastable atomic beams sent in vicinity of surfaces; the SAI team uses high-resolution laser spectroscopy to study excited atoms of a vapour close to a surface. A common interest is the long-range "Casimir-Polder" atom-surface interaction yielding in the van der Waals regime a rapid spatial dependence (in z-3 for a plane interface with z: atom-surface distance). The extension of the probed region spans from few nm for atomic beams to ~100 nm for optical techniques. The interfaces can be nanostructures (nano-gratings with atomic beams, artificial opals for optical techniques), or are well controlled for flat surfaces (super-polished sapphire), when the knowledge of the surface modes (polariton) - possible thermally populated - becomes critical.

We study a slow velocity atomic beam tuneable betwween 10 and 150 m/s through a nanograting of 50 nm width. We measure geometrical diffraction and at slow velocity the Casimir Polder potential between atoms and nanobars becomes predominant. The advantage is to constrain the theoretical model.

The team is specialized in sub-Doppler linear laser spectroscopy of an atomic -or now molecular- vapour confined in the vicinity of a wall or in interstices. A notable interest is for Casimir-Polder interaction (near-field van der Waals regime), including for a vacuum at a nonzero temperature.